comatoastWS6

well.. Just bught the car less than a week ago, and am already getting a scare.. Never noticed this when i test drove it twice, nor th day I picked it up ( one of the days was a cold start )


its not bad, but is bothering me.. I went to show my mechanic yesterday, but of course the car was plenty warm, and didn't make a sound.. This morning I took a quick video, and really need to know if its something to worry about.. To me it sounds like its coming from up top , but then again I am 50% deaf so alot of things sound muffled anyways lol


ANy ideas, suggestions or concerns? any tests I can run?

Oil looks good, and nothing is leaking from anywere,

thanks everyone




https://www.youtube.com/watch?v=gXu7...ature=youtu.be

2kgtp

Mine on cold starts sounds about the same, just not as loud sounding as yours. I was told its piston slap and that alot of ls1s so it. Mine seems to be worse when i get closer to oil change time.

comatoastWS6

Thank you for the reply! Any real fix for it?

josh4ku

iTrader: (10)

How many miles?

comatoastWS6

114k... I will say the video does sound worse than in person.. It really amplifies the knock

98CayenneT/A

Would you say it sounds like a knock or more of a tick? It's hard to tell sounds from cell videos cause everything is amplified

comatoastWS6

Sounds like a knock to me. A lifter tick is lighter and doesn't sound as... Heavy?? Lol forgive me, like I said my hearing is shot so it always sounds muffled to me. So... To "me" it sounds more like piston slap than a lifter tick

Russ K

iTrader: (1)

Definitely piston slap. Seen a lot of engines with piston slap that lasted quite a while if driven gently till operating temp.

Russ Kemp

98CayenneT/A

My guess would be mild piston slap, if it was a tick maybe lifter or injector tick, a knock does not usually go away after it is warmed up and usually gets worse/more pronounced in sound once warm

CAMSTER

iTrader: (10)

If the car is under warranty take it back if not....

I believe the tick comes from the top...

It likely be one of two things imo;

A valve seat came off and getting hit by the piston.

A lifter follower chewing on the cam.

The ladder may mess up the block if you continue to run it.

Find out which side is coming from and take valve cover off, see if any of the rockers is loose (moves around easy) this will tell where the problem is. Remove the rockers and inspect rockers and push rods in case of a bend push rod, if all the above is ok remove the head and lifters inspect them.

Let us know how it went...

nancygrl

That is hard to tell from the video. If possible leave the car overnight with your mechanic that way he can hear it 1st thing in the morning.

comatoastWS6

Hmmm those are some serious issues. Most of which I would think would continue to "knock" when warmed up? My knocking goes away after warmup...

I don't have the room or the knowledge to tear this thing apart either. Lol. I'd make it worse.

vettenuts

iTrader: (4)

Sometimes carbon build-up can tip the piston during cold start. You could try a de-carbonizing procedure to see if it helps. If it is piston slap, just don't push it until the noise disappears. I had it on a 1994 Pontiac Grand-Am. Sounded like a diesel on cold start, but the motor went 250K miles and still ran good when the body gave out due to rust.

nancygrl

I've heard of that also.....I've got slight piston slap going on at cold start up too, goes away in about 4-5 minutes. Going to have my mechanic do a top end cleaning procedure tomorrow and see if that helps it out any.

All the performance shops I've talked to say not to worry, just go easy 'til it goes away.

ls1 1990 VN

Hone & 3905 forged pistons or better still.. Stroker time

comatoastWS6

Is this decarbonizing basically just a seafoam treatment? Pulling off the booster line and sucking it into the intake?



Yea it does go away , from what I can tell , completely in about 10 minutes.. Still bugs me, but better knowing Im not the only one

comatoastWS6

haha .. One day

comatoastWS6

Also got a few pics of the car all cleaned up!!


https://ls1tech.com/forums/introduct...rthern-mn.html

kinglt-1

iTrader: (26)

It's piston slap and it is completely normal with Gen 3 motors.

comatoastWS6

Just one more question. It seems I can let the engine idle and warm up to 190* til I run thru a tank of gas , but the slap doesn't go away until you drive it for a few miles. What Does putting a load on the motor have anything to do with it? Does the piston expand that much under a load vs idle?

I've seen piston #7 is usually the one that takes the most abuse, and even tho its a common issue with ls1s, it actually has stopped me from doing heads and cam until I get a second or third opinion, because to me even tho it feels OK, I wouldn't consider a loose piston a healthy motor for internal mods..

Oil pressure seems good around 60 psi on cold start and under load. 40 psi or so at idle when warm